| 摘要 |
PURPOSE:To suppress noise due to the surface irregularity of a metallic substrate and to detect foreign matter by coloring a resist coating layer and using light which has wavelength absorbed by the resist coating layer as detection light. CONSTITUTION:When the resist coating layer 11b of a base material is irradiated with the detection light 12 which is so colored that the light is absorbed by the resist coating layer for foreign matter detection, the detection light 12 is absorbed by the resist coating layer 11b. Therefore, even if the surface of the metallic substrate 11a below the resist coating layer 11b is rough and uneven, a little scattered light is generated by the unevenness and the surface of the resist coating layer 11b is small, so little is scattered by the surface. Namely, little noise is generated by the surface roughness of the metallic substrate 11a or resist coating layer 11b. If foreign matter 13 is present on the surface of the base material 11, the foreign matter is irradiated with the detection light 12 to generate scattered light. Consequently, the detection signal of a detector 16 has a large projection at the part A where the foreign matter is present and the noise is suppressed to securely detect the foreign matter. |
